John Kerry's wife, Teresa Heinz Kerry, was taken by ambulance to a hospital on the Massachusetts island of Nantucket on Sunday with an unspecified medical condition.

A spokesman for the hospital, Noah Brown, said 74-year-old Heinz Kerry came to the facility in critical condition, and remains that way, although she has been stabilised.

The source close to the family said: "She was stricken around 4pm and taken away by ambulance to the local hospital. He (Kerry) is with her."

The source decline to provide details on Heinz Kerry's health other than to say that her trip to the hospital from the family's home was necessitated by a "medical condition" rather than an accident.

Kerry and his wife have long vacationed on Nantucket, an island about 30 miles off the south coast of Cape Cod, where many wealthy Americans – from hedge fund managers and executives to the heirs of New England fortunes – have summer homes.

Heinz Kerry is the widow of former US senator John Heinz, heir to the Heinz ketchup fortune.